Over 15,000 policemen are on duty in Chennai.

CHENNAI -- A dawn-to-dusk bandh called by several farmers and traders bodies over the raging Cauvery dispute began today across Tamil Nadu amid tight security with Opposition parties, including the DMK, supporting it.

As those who had given the bandh call have said a series of protests, including "road and rail roko", will be held, thousands of police personnel have been deployed across the state to maintain law and order.

Police said tight vigil was being maintained and no attempts to mar public peace or disruption of free movement of transportation -- on road or rail -- would be allowed.

Several local grocery shops, which usually open by daybreak, remained shut in view of the protests.

Police have sworn to maintain a tight vigil to make sure that there are no attempts to mar public peace.

State transport corporation-run buses besides trains are being operated as usual though autos, taxis and commercial freight operators remained off the roads.

The bandh has been called in protest against the violence targeting Tamils in Karnataka and also to seek Cauvery water for the state.

Barring the ruling AIADMK, its allies and trade unions affiliated, all other Opposition parties, including the DMK, Tamil Nadu Congress, DMDK, MDMK, Left parties and the PMK, are supporting the bandh.

Thousands of police personnel, including armed reserve forces, have been deployed in Tamil Nadu and in Chennai over 15,000 policemen are on duty.

Protection was being provided for Karnataka-related business establishments, schools, institutions and areas where Kannada speaking people live, including Krishnagiri district.